KR20030004368A - Refractory component and assembly with improved sealing for injection of an inert gas - Google Patents

Abstract

The invention relates to a fire resistant component (1) provided with means for injecting or conveying gas (5, 16) and means for delivering gas from the outer wall of the refractory component (5, 16) to the means for injecting or conveying the gas. 4, and an assembly comprising the refractory components and gas delivery paths 9, 19 as described above, wherein one end of the gas delivery path comprises a seal 12, 22 with respect to the side wall face of the expanded cross section. ) Into an enlarged cross-section that keeps the pressure pressed.

Description

Refractory components and assemblies for inert gas injection with improved sealing {REFRACTORY COMPONENT AND ASSEMBLY WITH IMPROVED SEALING FOR INJECTION OF AN INERT GAS}

It is known that continuous casting of liquid metal is generally carried out by means of an installation consisting of various refractory components forming a passage between two successive metallurgical vessels. These refractory components perform a variety of functions, such as the transport, cooling and the protection of the liquid metal against chemical attack from the ambient atmosphere, and, if necessary, the regulation of the injection flow rate of the liquid metal. For example, these components may be internal nozzles supported on a well block integral with the bottom of the upper metallurgical vessel, submerged inlet nozzles or injection protection plates, collection nozzles, or fixed plates of slide valves, or It may be a movable plate.

The bonding surface between these various components forming the injection passage all constitute potential entry points of ambient air. In fact, due to the flow of liquid metal through this injection passage, a substantial negative pressure is created which contributes to the air entering through these bonding surfaces. The detrimental effects of this air (nitrogen and oxygen) ingress on the quality of cast metals are known, and efforts to solve them have been raced for a long time.

One solution known in the state of the art involves injecting an inert gas such as argon into the bonding surface between two adjacent refractory components in the injection passage. Such spraying may be done at the surface of at least one of the refractory components, for example, via a groove formed for this purpose. To be effective, the groove should enclose the injection orifice as far as possible to prevent the inert gas under positive pressure from entering the air into the injection passage. Recently, an improvement to this system has been to keep the sealant suspended in a carrier fluid (which may be an inert gas) so that any sealing defects that are likely to occur between two adjacent surfaces during casting are immediately removed. Further spraying is proposed in international patent application WO 98/17421.

Another solution known in the state of the art involves the direct injection of an inert gas into the injection passage to form a barrier against contamination by ambient air along the entire length of the injection passage. In this case, injecting the inert gas into the liquid metal generally involves diffusion through the porous wall of the component formation of the injection passage, or in another known variant, one or more orifices in the form of openings or slots arranged around the injection passage. By diffusion through.

Furthermore, a method of injecting an inert gas directly into the injection passage so that the inert gas mechanically cooperates with the liquid metal is also known. The purpose of this type of inert gas injection is to be located downstream of the injection point, particularly for the erosion of liquid metal flow, such as the edge of the injection orifice of a slide valve movable plate designed for flow control. It may be to protect the erosion of sensitive refractory components. Another known effect of injecting inert gas into the injection passage is to reduce the clogging problem of the injection passage. In fact, problems due to the formation of alumina deposits on the walls of the injection passage have been known for a long time, especially in the case of casting of alumina-killed steel. Thus, inert gas injected downstream of the point where this kind of blockage can occur mechanically or thermally isolates the liquid metal from the injection passage, thereby preventing or reducing the formation of such deposits.

Finally, it is also possible to inject a gas for the purpose of cooling the refractory component in question. It should also be noted that the present invention relates to a refractory component used to inject gas into the bottom of a metallurgical vessel containing a molten metal bath, for example a porous plug.

Therefore, for the purposes of the present patent application, the expression "injection of gas" refers to the direct injection of an inert gas into the injection passage or the bottom of a metallurgical vessel, and through the groove at least partially surrounding the injection orifice of liquid metal. Two injections of injecting an inert gas (or sealant suspended in a carrier fluid as described in international patent application WO 98/17421) into the bonding surface between two adjacent refractory components, or the injection of cooling gas Say.

Refractory components designed for the injection of an inert gas generally comprise means for delivering the gas (via the groove or injection passage) to the injection means. However, the delivery means and injection means of the gas are provided by adjacent intercommunication components (these may be separated by intermediate refractory components, the main feature being that the gas can be transferred from the delivery means to the injection means). Assemblies of refractory components are known. For the purposes of the present patent application, when referring to a refractory component provided with a gas delivery means and an injection means, it is different from a refractory component comprising both the gas delivery means and the injection means, or a gas delivery means. It is equally referred to a component provided with transmission and / or communication means for the injection means that may be provided by the refractory components.

The delivery means generally comprise an introduction hole which is open on the outer wall of the refractory component and connected to the gas delivery path. The delivery path is connected to the stationary gas supply circuit of the casting plant via a flexible pipe which is protected from heat radiation. Conventionally, during fabrication of the refractory component, a metal connector is mounted in the injection hole, wherein the connector and the material form an integral assembly upon sintering of the refractory material component of the component. Next, the coupler is screwed (the coupler is joined by a male thread projecting past a fireproof component screwed to the female end of the gas delivery path, or the coupler is connected to a female screw connected to the male end of the delivery path. Can be connected to the gas delivery path by welding or by various mechanical connection means. These gas delivery means are, firstly, not clear that threaded joints, in particular joints that remain tight at very high temperatures that the casting installation receives during casting operations, can be made airtight, and secondly, Due to the difference in the expansion coefficient between the metal and the refractory material used in the production, it is not entirely satisfactory in that it is inevitable that the sealing tightness between the connector and the refractory material gradually deteriorates. The negative effect of the loss of the hermetic seal is triple. That is, firstly, it is well known that the injection volume of gas is much higher (the price of inert gas such as argon is expensive), and secondly, as pointed out above, the entire injection passage is under negative pressure with respect to the surrounding atmosphere. There is a risk that air can enter through these defective joints. Third, if the seal tightness is compromised, accurate control of the injection volume of the gas actually injected into the system will be lost and a completely reproducible system will be produced. It is impossible to establish.

For example, the "packing" of refractory components in a metal casing containing openings in a connector, i.e., a welding method to ensure the mechanical maintenance of the connector and to improve airtightness, may be used to improve such circumstances. Attempts have been made. Many shortcomings related to this "improvement" have already been reported. For example, since the connector is integral with the metal casing, the connector tends to loosen from the refractory material and move around in its seating, which leads to loss of inert gas and the aforementioned As a result, air is introduced into the liquid metal.

More recently, a very simple device for delivering inert gas to an internal nozzle has been presented in European patent application EP 703,028, in which a connection fastening is connected in which the outer surface of the refractory component containing the gas feed is connected to the inert gas delivery path. The sphere simply contains a gas introduction hole in which the sphere is held in a pressurized state. If desired, it may be possible to provide a seal between the fastener and the inlet.

Although the device greatly improves on such a situation, the Applicant believes that the airtight seal between the connection coupling portion and the gas inlet hole on the surface of the refractory component, even when the sealing portion is engaged between the connection coupling portion and the introduction hole. It was observed that Tao is not yet fully satisfactory in that it is not entirely guaranteed.

The refractory component comprises means for injecting or conveying gas and means for delivering gas from the outer wall face of the refractory component to the injector means, the gas delivery means being extended from an outer wall face of the refractory component. A cross section and one end in communication with the inner end of the expanded cross section and a reduced cross section in communication with the means for injecting or transporting the gas at the other end, wherein the fire resistant component is coupled to the inner end of the expanded cross section. Refractory components are known from FR-A-2,763,012 which comprise a sealed seal, the seal comprising an orifice in communication with the orifice in communication between the expanded cross section and the reduced cross section. .

Because of this special refractory component arrangement, the gas delivery path can be more deeply engaged with the refractory component, so that when fitting a suitable seal therein, the seal tightness is not only in the communication between the two parts of the delivery means. It is also guaranteed on the walls of the expanded cross section. It has been observed that the seal tightness is very substantially improved (reduced inert gas consumption, reduced air intake and precise control of gas injection amount) compared to the device disclosed in European patent application 703,028. However, there is still a need for improvement of the hermetic seal.

FIELD OF THE INVENTION The present invention relates to refractory components for use in the processing of molten metal, such as steel, with a gas supply and improved sealing. In particular, the present invention relates to refractory components for use in continuous casting of molten metal.

BRIEF DESCRIPTION OF DRAWINGS To describe the invention in more detail, two exemplary embodiments, which are set forth as non-limiting examples, are described below with reference to the accompanying drawings.

1 is an axial sectional view of an internal nozzle,

FIG. 2 is an enlarged view of a circle I portion in FIG. 1,

3 is an axial cross-sectional view of the slide valve plate.

According to the invention, the seal provides a cross section substantially similar to the expanded cross section. Thus, when the seal is put in a compressed manner in an appropriate manner, the seal not only supports the end of the expanded cross section but also supports the side wall surface of the cross section, thus providing a much stronger seal.

It is advantageous that the thickness of the seal does not exceed the depth of the expanded cross section, otherwise the plastic seal under compression effect by the gas delivery path will support the rim of the outer orifice of the delivery means as it deforms, The seal tightness at the inner end of the expanded cross section is no longer guaranteed.

Of the present invention According to certain embodiments, the inner end of the expanded cross section forms a surface that provides an orifice, and the expanded cross section and the reduced cross section communicate with each other via the orifice. In this way it is possible to use a gas delivery path that is essentially tubular.

It is advantageous to construct the expanded cross section with a bore of substantially circular cross section which is easy to manufacture.

A facility may also be provided to level the surface forming the inner end of the expanded cross section and to be substantially orthogonal to the axis of the bore. Not only is such a device easy to achieve, the sealing hermeticity is also improved when the device is made by the pressing of parallel refractory components.

According to certain embodiments of the invention, the thickness of the seal does not exceed the depth of the expanded cross section. It should be noted that the seal can be made integral with the refractory component.

It is advantageous for the seal to provide a cross section substantially similar to the expanded cross section. Thus, when the seal is placed in a pressed manner in an appropriate manner, the seal not only supports the end of the expanded cross section, but also supports the side wall surface of the cross section, thereby providing a much more airtight seal. It is essential that the thickness of the seal does not exceed the depth of the expanded cross section, otherwise the plastic seal under the compressive effect by the gas delivery path will support the rim of the outer orifice of the delivery means as it deforms and expand The hermetic tightness at the inner end of the cross section is no longer guaranteed.

The seal preferably takes the form of a washer. However, such a washer layer can be provided according to the required thickness of the seal. Those skilled in the art will readily determine the optimum seal thickness.

It is advantageous to fabricate the seals from a plastics material so that when the pressure is applied at the operating temperature, the seals are sufficiently deformed to form an airtight seal with the bottom wall and sidewall surfaces at the ends of the expanded cross section. Clay and graphite are suitable materials possible for such use, and it is better to choose graphite.

According to another embodiment, the present invention is directed to an assembly comprising a refractory component and a gas delivery path as described above, wherein one end of the gas delivery path is sealed against the inner end and sidewall surfaces of the expanded cross section. Meshes with an extended cross-section that keeps the part compressed. The advantages of this assembly have already been described above.

According to certain embodiments of the invention, the refractory component is associated with a metal casing (eg in the case of an internal nozzle) or a band (eg in the case of a slide valve plate) covering at least partly in the region of the gas delivery means. . Thus, by forming a secure attachment between the delivery path and the casing or band (by welding or screwing), it becomes possible to avoid inadvertent loss of sealing hermeticity, for example in the case of vibration.

An end of the delivery path that engages the expanded cross section is advantageously configured to form a hermetic engagement with the seal. For example, the ends may be shaped into cones or truncated cones to “key” into the engagement portion. As a variant, the end of the delivery path may be shaped in a spiral form such that the delivery path is "screwed" in the engagement portion. A self-tapping end may also be provided so that a perfect engagement helix is formed in place in the seal and the delivery path / sealing engagement is entirely airtight. According to this variant, the action of screwing the end of the delivery path into the seal advantageously presses the seal towards the side wall of the expanded cross section.

Finally, according to the most particular embodiment of the present invention, since the expanded cross section is sufficiently deep, the pressing force of the seal increases under the effect of thermal expansion of the end of the delivery path that engages the expanded cross section. In fact, if the delivery path is rigidly constructed with a casing or band, the only possibility of expansion is towards the end of the expanded cross section in which the seal is located.

1 shows an assembly of an internal nozzle 1 consisting of a refractory body 2 forming an injection passage 3 and a plate 4. This internal nozzle 1 also contains gas injection means for injecting a gas, for example an inert gas such as argon, into the injection passage 3. These gas injection means are formed, for example, by a sleeve 5 of porous material mounted in a groove 6 molded in the fire-resistant body 2. This groove 6 is connected to the gas delivery means 7, 8. As shown in FIG. 1, these delivery means may appear on the upper surface of the plate 4. Part of the gas delivery path 9 is also shown with a metal casing 10 which also surrounds the plate 4 of the inner nozzle.

2 shows in detail the connection between the gas inlet and gas delivery means in the plate 4 of the inner nozzle. These gas delivery means comprise an enlarged cross section 7 and a reduced cross section 8 which communicate via the orifice 11. The inner end of the expanded cross section is engaged with a seal 12 of graphite, for example. Also shown is one end of the gas delivery path 9 which engages the expanded cross section 7. This transmission path 9 shows that the circular welding part 13 is firmly manufactured with the casing 10.

3 shows the fireproof plate 14 of the slide valve provided with the metal injection orifice 15. The refractory plate encloses a metal injection orifice 15 and has a circular shape for forming a gas injection passage between the adjacent refractory portions together with the surface of the refractory portion (not shown) adjacent to the refractory plate 14. The gas circulation groove 16 is provided. The groove 16 is connected with gas delivery means comprising an expanded cross section 17 and a reduced cross section 18 communicating via an orifice 21. Also shown is a gas delivery path 19 that engages the expanded cross section and is rigidly fabricated with the metal band 20 of the fireproof plate 14 by the spot welds 23. When this refractory plate is in operation, under the influence of the rising temperature of the assembly, the portion of the gas delivery path 19 between the spot weld 23 and its inner end expands toward the inner end of the expanded cross section 17. Press the seal 22.

reference mark

1: internal nozzle

2: fireproof body

3: injection passage

4: Edition

5: porous sleeve

6: home

7: expanded cross section

8: reduced cross section

9: gas delivery path

10: metal casing

11: communication orifice

12: sealing part

13: circular weld

14: fireproof board

15: Orifice for metal injection of fireproof plate

16: gas circulation groove

17: expanded cross section

18: reduced cross section

19: gas delivery path

20: metal band

21: communication orifice

22: sealing part

23: spot welding

Claims (12)

Means are provided for delivering gas to the means 5, 16 for injecting or conveying the gas and to means 5, 16 for injecting or conveying the gas from the outer wall of the refractory component, and the means for delivering the gas Means for communicating with the inner end of the expanded cross section (7, 17) and at one end with an extended cross section (7, 17) extending from the outer wall surface of the refractory component and for injecting or transporting gas at the other end ( Consisting of reduced cross sections 8, 18 in communication with 5, 16, wherein the fire resistant component further comprises seals 12, 22 engaged with an inner end of the expanded cross section; The parts 12, 22 are characterized in that the fire resistant component 1, 14 comprises an orifice that at least partially mates with the orifices 11, 21 communicating between the expanded cross section and the reduced cross section. , The sealing component (12, 22) is characterized in that it provides a cross section substantially similar to the expanded cross section (7, 17). 2. The inner end of the expanded cross section (7, 17) according to claim 1 forms a surface providing an orifice (11, 21), the expanded cross section (7, 17) and the reduced cross section ( 8, 18 are fireproof components characterized by communicating via these orifices (11, 21). 3. Refractory component according to claim 1 or 2, characterized in that the expanded cross section (7, 17) consists of a bore of which the cross section is substantially circular. 4. Refractory component according to claim 3, characterized in that the surface forming the inner end of the expanded cross section (7, 17) is flat and essentially perpendicular to the axis of the bore. 5. The fire resistant component according to claim 1, wherein the thickness of the seal (12, 22) does not exceed the depth of the expanded cross section (7, 17). 6. 6. Refractory component according to claim 5, characterized in that the seal (12, 22) consists of one or more washers of plastic material. An assembly comprising the refractory components (1, 14) and gas delivery paths (9, 19) according to claim 5 or 6, wherein one end of the gas delivery path is the side of the expanded cross section (7, 17). Assembly to keep the seal (12, 22) pressed against the wall. 8. The fire resistant component according to claim 7, which is provided with a metal casing 10 or band 20, The gas delivery paths 9, 19 pass through the casing or band or abut the casing or band, And wherein the gas delivery path and the casing or band are securely connected. 9. An assembly according to claim 7 or 8, characterized in that the end of the gas delivery path (9, 19) engaging the refractory component is configured to form an airtight bond with the seal (12, 22). 10. The assembly according to claim 9, wherein the end of the gas delivery path (9, 19) that engages with the refractory component comprises a spiral that engages the seal. 10. The assembly according to claim 9, wherein the end of the gas delivery path (9, 19) that engages the refractory component is shaped into a cone or a truncated cone that engages in the seal (12, 22). 12. The expanded cross section 7, 17 according to claim 7, wherein the expanded cross section 7, 17 is of the part of the gas delivery path 9, 19 engaged in the expanded cross section 7, 17. An assembly characterized in that its depth is sufficiently deep such that the sealing portion (12, 22) is compressed with respect to the inner end and sidewall surfaces of the expanded cross-section under the expansion effect.